1. Field of the Invention
The present invention relates to a catalytic composition based on a grafted metal oxide, to its preparation and to its use in a process of polymerization by opening oxygenated rings.
2. Description of the Related Art including information disclosed under 37 C.F.R. 1.97 and 1.98
Polymerization by opening oxygenated rings, for example lactones or lactides, is well known. Metal alkoxides are used as initiators, for the reaction. These initiators are used in homogeneous medium and they have been found to be effective. However, they have drawbacks. Firstly, their solubility is low. In addition, during their use, aggregations of the alkoxide molecules occur, leading to the existence of several families of active centres, which has the consequence of producing a wider molecular mass distribution of the polymer obtained. Finally, it is occasionally difficult to separate the initiator from the polymer formed, thereby compromising the purity of this polymer.
It would thus be desirable to have available a heterogeneous catalyst.
One object of the invention is to provide such a catalyst.